Including Sound in Your Scene

Learn how A-Frame's sound component, with properties like autoplay, loop, and volume, can be used to create immersive audio experiences in XR environments.

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Sound is crucial in creating a realistic and engaging user experience for our virtual environments. The importance of sound in XR lies in its ability to enhance the user’s sense of presence and immersion. Here are some specific ways in which sound is essential in XR:

  • Spatial audio: By providing audio cues that match the user’s location and orientation in the environment, spatial audio can create a more realistic and immersive experience. This can help the user locate and identify objects, navigate the environment, and feel more fully immersed in the virtual world.

  • Realism: In many XR applications, the goal is to create a realistic and believable environment. Sound can help achieve this by providing a layer of detail that enhances the user’s sense of immersion.

  • Interactive feedback: Sound can communicate important information to the user, such as alerts, instructions, or feedback. This can be crucial for safety and effectiveness in some XR applications, such as industrial training simulations or medical applications.

  • Emotional impact: Sound can also create a mood or emotional impact in XR experiences. By using music, ambient noise, or other audio cues, developers can enhance the user’s emotional engagement with the experience.

  • Accessibility: By providing audio cues and descriptions at key moments in the VR experience, developers can make A-Frame experiences more accessible to visually impaired users.

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A sound wave
A sound wave

Overall, sound is a critical component of XR and can significantly impact the user’s sense of presence, immersion, and overall enjoyment. We’ll learn how to use the sound component in A-Frame to enhance the user’s sense of presence and immersion and create entertaining and informative experiences.

The sound component

In A-Frame, the sound component provides the following properties and functionalities:

  • autoplay: Can be used to play sound automatically.

  • loop: If selected, the sound can continue to replay in a loop.

  • maxDistance: Maximum distance between the audio source and the listener, after which the volume is not impacted, i.e., would not be reduced any further.

  • refDistance: In distance-based audio attenuation, this property defines the reference distance at which audio attenuation begins. It’s a critical parameter for simulating how sound fades as the listener moves away from the source.

  • rolloffFactor: It is integral to distance-based attenuation; this property controls the rate at which sound fades as the listener moves away from the source.

  • distanceModel: linearResults in a constant rate of volume reduction as the audio source moves away from the listener., inverseOffers an attenuation behavior where the volume increases as the listener moves closer to the source. This can be useful for creating unique auditory effects, such as "zooming in" on sounds as the listener approaches the source., or exponentialProvides more control over attenuation behavior, allowing you to fine-tune the rate of volume reduction..

  • on: An event the entity listens to before playing sound.

  • poolSize: This attribute specifies the number of simultaneous instances of this sound that can be played together.

  • positional: Determines whether or not the audio is positional (movable).

  • src: This attribute contains a link (or URL) to the audio file.

  • volume: How loud the audio should be.

When we attach the sound component to an entity in the scene, the entity becomes the source of the sound or audio.

To demonstrate the use of sound, we contextualize the car we built in earlier lessons in a city“Small Street in Shade.” n.d. Texturify.com. Accessed December 18, 2023. https://texturify.com/stock-photo/small-street-in-shade-10126.html. environment. When you drag the cursor and click the car in the scene below, you will hear the sound“Freesound - Pleasant Pluck Dry.wav by ZoviPoland.” n.d. Freesound.org. Accessed December 18, 2023. https://freesound.org/people/ZoviPoland/sounds/573286/. attached to the car.

  • In the code above, we attach the sound component with the car entity. We set the on property to click so that the sound plays whenever we click the entity. We can configure the on property to any event on which we want to play the sound.

  • Moving around in the scene using the WASD keys, we see the positional property in action. This property is set to true by default. When we move away from the car, we’ll observe that the volume of the sound reduces with distance from the camera.

  • We can also change the refDistance to any value. This value will determine the distance after which the sound’s volume will reduce.

Sometimes, we might want to place the sound at a specific offset with respect to a given entity to make the experience of that sound in the scene more realistic. We can do this by nesting the sound component as a child entity with the parent. So, in our example, this would look something like:

<a-entity id="car">
  <a-entity sound="src:#positional"></a-entity>
  ....
</a-entity>

Now, we can position this invisible entity with the sound component at the location of our choice, either by setting the position using A-Frame Inspector or by specifying the position property in the A-Frame code.

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Positioning sound in an entity
Positioning sound in an entity

Let’s move on to the pause and resume functionality.

Pause and resume

We can also pause, resume, and stop the sound using the playSound(), pauseSound(), and stopSound() functions of the sound component. We’ll use two icons (pause and play) to control the car’s sound. For the icons, we’ll use the <a-image> primitive. We also create two components called play and pause that control the sound“Freesound - Car Ignition, Exterior, A.wav by InspectorJ.” n.d. Freesound.org. Accessed December 18, 2023. https://freesound.org/people/InspectorJ/sounds/338954/. of the car. The following example shows the working: align the cursor with the respective option to test the working. Click the “Run” button to launch the experience.

  • In the play component, we first select the car entity using the document.querySelector() function and store it in myEl. We attach an event listener to the entity to which this component is attached to listen for click events.

  • We attach the play component to the <a-image> play primitive. So, whenever the car entity is clicked, the play component plays the sound on the car entity.

  • A similar functionality is used in the pause component and the pause icon.

  • We also set the loop property to true for the sound component on the car entity.

Conclusion

We’ve comprehensively understood the fundamental functionalities of utilizing sound to elevate the immersive quality of your XR scenes. Next, we’ll learn about adding videos to our virtual scenes.